John Allman of the California Institute of Technology thinks that much of this social deficit may come down to a lack of a special class of spindle neurons, sometimes called Von Economo neurons after their discoverer, who made the observation in 1925. Spindle neurons consist of a very large bipolar neuron that is found only in the frontoinsular and anterior cingulate cortex and thought to provide the interconnection between brain regions that are activated by social learning. This location may explain why spindle neurons have been found solely in species that are particularly social, including all the great apes, elephants, and whales and dolphins.
Humans have the biggest population of spindle neurons located in the frontoinsular and anterior cingulate cortex areas—the same regions that may be disrupted in autism spectrum disorder. Spindle neurons are thought to work by keeping track of social experiences, leading to a rapid appreciation of similar situations in the future. They provide the basis of intuitive social learning when we watch and copy others. It may be no coincidence that the density of spindle neurons in these social regions increases from infancy to reach adult levels somewhere around the fourth birthday in typical children, the watershed when most child development experts agree that there is noticeable change in social intuition skills. This may also explain why individuals with autism, who have disrupted frontoinsular and anterior cingulate cortical areas, have difficulty working out what the rest of us just know without having to think very much.
This article was originally published with the title Knowing Me, Knowing You.